U 87

Description

The U 87 was designed as a solid-state version of the U 67 tube microphone. It retained the K67-style capsule of the U67, but replaced the tube amplifier circuit with a FET/transformer design. In short, the U87 was a tripolar FET condenser with a transformer-coupled output. A switch below the headbasket allowed selection of Cardioid, Omni, or Figure-8 patterns. U 87i, U 87A iThe mic’s capsule, called the K87, was a center-terminated, dual-backplate, dual-diaphragm 34mm design, like the K67. It differed from the K67 in three acoustically-transparent respects:

the K87’s two backplates were electrically isolated from one another,

and it therefore connected to the amplifier circuit by four wires rather than three.

The capsule mounting screws were “sleeved” to prevent an electrical connection between backplate halves.

These changes were required to support the Figure-8 polar pattern, which otherwise would have required more power than the 48V phantom power supply could provide (without a DC-DC converter).
Note that both the K67 and K87 capsules used a 40-micron spacer between the two backplate halves. In the K67, the spacer is aluminum. In the K87, the spacer is made of (non-conductive) plastic. The K67 (now called K870/67) and K87 capsules are said to be mechanically and acoustically identical.
The K87 capsule was designed for a 60V polarization voltage, but was run in the U87(i) at ~46V; as a result, the U87(i) had ~10mV/Pa lower sensitivity, and 3dB lower signal-to-noise ratio than the AB-powered U77 or the revised U87, called the U87A(i), both of which employed a DC-DC converter to produce a ±60V supply for the capsule.
U 87 i CircuitThe body of the U87(i) housed an optional pair of 22.5V batteries. This space was repurposed to store a DC-DC converter when the U87A(i) was developed in 1986.
The mic’s output impedance was 200Ω. It could be changed to 50Ω by the user; this modification required a solder gun, according to Neumann literature.

...X and Robert Lang
At my little studio I had B-average AD/DA conversation with an SSL AlphaLink AX. I used a Neumann U-87 for damn near everything because that was my only good condenser, and a Neve Portico 5032 pre-amp for pretty much everything as well. All of the recording was done in this little...

I was going to write, "just buy the cheapest, dented up, painted, original U87 you can find and use that". That's what I did.
But after a quick search I found out that there is no such thing anymore! Dented up studio workhorses are advertised at $2500.